Former International Monetary Fund (IMF) chief Dominique Strauss-Kahn is fiercely defending himself against allegations he was involved in an organised gang that hired prostitutes for hotel orgies.

Investigators are looking into whether the 62-year-old was aware he was dealing with prostitutes and pimps when attending sex parties in Lille, Paris and Washington in 2010 and 2011.

Mr Strauss-Kahn admits attending the sex parties, which were organised by business acquaintances, but says he did not know prostitutes were there.

The 62-year-old, who has now been released on bail, could face up to 20 years in prison if tried and convicted.

Lawyers for the disgraced former IMF boss say he is being hounded for his "libertine ways" and say they will challenge the judicial inquiry into the alleged offences.

"We are convinced a great injustice has been committed," lawyer Henri Leclerc said.

Mr Leclerc, himself a former finance minister and former head of the IMF, says his client participated in two or three of the gatherings a year over five years "with friends, and women who were friends of his friends".

"Everyone can say whatever they want about the moral side of it. But that doesn't mean it's forbidden anywhere in the penal code," he added.

"In reality, what he's being pursued for here is something like an offence of lust."

Even if Strauss-Kahn knew the women were prostitutes, it would not be illegal in France to pay for their services.

However, magistrates are investigating whether he participated in complicity in a pimping operation, accusations Mr Leclerc describes as "nauseating".

Text messages supposedly sent by Mr Strauss-Kahn to his friends could form the crux of the legal case. The messages, which referred to upcoming "soirees" and the women who would be there, might be interpreted as meeting the threshold of complicity in pandering, according to an anonymous source.

Under French law, that legal definition of pimping is "helping, assisting, or protecting prostitution, taking profit from prostitution ... hiring, training or leading someone towards prostitution."

Mr Strauss-Kahn has been released on bail of 100,000 euros ($122,000), and forbidden to contact witnesses, the press, and others involved in the case.

Eight people have already been arrested in the case, and construction firm Eiffage fired an executive suspected of using company funds to hire sex workers.

Mr Strauss-Kahn's former allies are starting to distance themselves, less than a month before the French presidential election, for which Mr Strauss-Kahn was once a front runner.

He resigned from the IMF last year after being accused of attempting to rape a New York hotel maid.

The criminal charges were later dropped, but the maid's civil case is due to start in New York on Thursday.

It's a fundamental human yearning to be a part of something bigger than one's self, and maybe that's what drove my mate Ash to die, far from home, in a bloody foreign war against Islamic State, writes C August Elliott.